The EAGeR trial was a multi-center, block-randomized, double-blind, placebo-controlled trial conducted across four medical centers in the U.S.. A total of 1228 women ages 18-40 years with up to two documented prior miscarriages and who planned to become pregnant again were randomized for this trial, making the EAGeR trial the largest preconception trial of LDA. Each woman was randomly assigned to 81 mg aspirin daily or placebo beginning prior to conception and continued to 36 weeks gestation in women achieving pregnancy. Participants were block randomized by study center and eligibility stratum, defined based on specific eligibility qualifications: 1) original stratum, women with exactly one documented pregnancy loss <20 weeks gestation during the preceding 12 months; and 2) expanded stratum, women not meeting all criteria for the original stratum, and having 1 or 2 prior pregnancy losses of any gestational age at any time in the past. Participants attended two study visits per menstrual cycle for the first two cycles attempting pregnancy and once per cycle thereafter, which included spot urine and blood sample collection. Follow-up ended after six menstrual cycles attempting pregnancy or, in women becoming pregnant, throughout pregnancy. This proposal is to request funding for the measurement of stored biospecimens in the EAGeR Trial. The assays proposed will provide a rich data source on biomarker levels that can be analyzed to answer novel research questions in conjunction with the extensive data already collected in the EAGeR Trial. A growing body of evidence suggests that exposure to many common environmental chemicals, particularly those with endocrine-disrupting properties, may be associated with impaired fecundability and increased risk of adverse pregnancy outcomes. The objective of this task is to measure several analytes in stored serum and urine samples from the EAGeR trial to investigate the association between environmental chemicals and ovulation, fecundability, pregnancy, and pregnancy loss.